U.S. Pat. No. 3,885,928, the disclosure of which is incorporated herein by reference, describes a recovery and purification system for processing the reactor effluent produced in the ammoxidation of propylene or isobutylene to produce acrylonitrile or methacrylonitrile. This system employs a quench column in which the hot gaseous reactor effluent is cooled by direct contact with water. As a result of this procedure, a liquid byproduct is produced which is continuously withdrawn from the bottom of the quench column.
This quench bottoms byproduct typically contains on the order of 10 weight percent ammonium sulfate, 16 weight percent of a heavy organic material, a slight amount of light organics and the balance (about 74%) water. Because of the heavy organic material which is composed of a mixture of different high-boiling organic compounds having a high degree of nitrile substitution and also containing some oxygenated hydrocarbon groups, the quench tower bottoms is essentially useless. Hence, it is usually disposed of either by burning or by deep welling.
Unfortunately, both of these disposal methods are becoming less and less attractive. With the increasing costs of fuel, burning of the quench tower bottoms becomes increasingly expensive. Moreover, burning is environmentally objectionable because of sulfur dioxide emissions. Deep welling is also objectionable from an environmental standpoint.
Accordingly, it is an object of the present invention to provide a new technique for disposing of the quench tower bottoms produced by an acrylonitrile or methacrylonitrile purification and recovery unit.